Runcorn was for 32 years the head of the Department of Physics at Newcastle upon Tyne University, until 1988 when, on reaching the official retirement age, he become attached to Imperial College London. He put Newcastle on the geophysical map. Overseas scholars converged to research there or to participate in wide-ranging Nato-sponsored international scientific discussion meetings during which they could enjoy the magnificent scenery of Northumberland as seen from Hadrian's Wall, admire the splendours of Durham Cathedral and York Minster, or sample Newcastle Brown in one of the many pubs, often with Runcorn as indefatigable companion and knowledgeable guide.
Runcorn was wedded to the promotion of geophysics by almost incessant lecture tours, but at no stage did he consider it necessary to hand over the headship of the Physics Department in Newcastle to one of the patient and hard- working members of his very able staff, with whom he kept in touch during long periods of absence by means of telephone calls and picture postcards from distant parts of the world.
He was born in Southport, Lancashire, in 1922, and attended the King George V Grammar School there before entering Gonville and Caius College, Cambridge, in 1940 to study Engineering. After taking his degree, he joined the Radar Research and Development Establishment at Malvern, Worcestershire, where he remained until the end of the Second World War. In 1946 he moved to a junior academic post in the Physics Department at Manchester University, spending his first year with a group working on cosmic rays before switching at the suggestion of P.M.S. Blackettt, his department head, to geophysics, the subject which became his abiding passion.
His allotted task was to determine how the Earth's magnetic field varies with depth, which involved carrying out magnetic measurements in deep coalmines in Kent, Lancashire and Yorkshire. The results would provide a test of a new theory of the Earth's magnetism that Blackett had just proposed. By 1950, the theory had been disproved not only by the "mine experiment" but also by the results of a delicate laboratory experiment Blackett conducted, requiring the construction of a very sensitive magnetometer. This instrument later enabled groups headed by Blackett and Runcorn to make important advances in the field of rock magnetism.
In 1950 Runcorn returned to Cambridge, where he spent six years as Assistant Director of Research in the Department of Geodesy and Geophysics. His own personal research was crucially influenced in 1951 by new results on polarity reversals of the Earth's magnetic field that were emerging from studies of the magnetism of Icelandic lava flows. In parallel with work already started by Blackett's group in Manchester, Runcorn orchestrated at Cambridge a vigorous programme of field and laboratory studies for determining the fossilised ancient directions of the Earth's magnetic field in sedimentary and igneous rocks from several parts of the world. This provided striking new evidence in favour of Alfred Wegener's celebrated but then controversial "continental drift" hypothesis, leading in the 1960s to the introduction by others of the highly successful theory of plate tectonics.
In 1956 Runcorn moved to a chair of physics at Durham University and headship of the Department of Physics at King's College, Newcastle upon Tyne - which later became the University of Newcastle upon Tyne.
Keith Runcorn celebrated his 73rd birthday in November, four months after his widowed mother attained the age of 100. Keen on physical fitness, he had played rugby until his mid-fifties, swam nearly every day, and never gave up squash.
On 5 December he was found dead in a ransacked hotel room in San Diego, California, a city he knew well. En route to the 1995 fall meeting of the American Geophysical Union in San Francisco after a few months at the University of Alaska at Fairbanks, where he held a visiting professorship, he was about to spend a few days in San Diego and Los Angeles with geophysicists of the University of California.
Stanley Keith Runcorn, geophysicist: born Southport, Lancashire 19 November 1922; Fellow, Gonville and Caius College, Cambridge 1948-55; Assistant Director of Research in Geophysics, Cambridge University 1950-55; Professor of Physics, Durham University 1956-63; Head of Department of Physics, Newcastle upon Tyne University 1956-88, Professor of Physics 1963-88; FRS 1965; Sydney Chapman Professor of Physical Science, University of Alaska 1988-95; Senior Research Fellow, Imperial College London 1989-95; died San Diego, California 5 December 1995.